Update on IMPROVE Light E

Equation and Natural Condition

Tom Moore, WRAP Technical C

May 23, 2006
OR .......

Defining Regional Haze Imp

Aerosol Sampling Da

AND .......

Knowing the unknowa
“Old” IMPROVE Light Extinctio

• Developed in late 1980’s –

consensus light ex

coefficients for species measured by IMPROsampler

• Adopted by EPA for “Tracking Progress” –

monitoring guidance documents are at: http://vista.cira.colostate.edu/improve/Publi

eDocs/guidancedocs.htm

• Equation is used to estimate light scattering 

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10

0.6

110

4

3

(

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(

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++

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×

+

×

×

≈

×

×

Coarse Mass

Fine Soil

Elemental Carbon

Organic Mass

f RH Nitrate

b

f RH Sulfate ext
“Revised” IMPROVE Light Extinc

• Review process by IMPROVE Steering Com

scientific community during 2005

• Findings of review prepared by Jenny Hand 

presented and discussed at: http://www.wrapair.org/forums/aamrf/meet

ndex.html

• Technical document describing revised equa

http://vista.cira.colostate.edu/improve/Publi

019_RevisedIMPROVEeq/RevisedIMPROVc

• Light extinction data from 2000 onward are 

available using old and revised equation on http://vista.cira.colostate.edu/views/ and the 

http://vista.cira.colostate.edu/tss/
“Revised” IMPROVE Light Extincti

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Coarse Mass

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Elemental Carbon

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Bottom line:

• New equation fitted to aerosol data colleclight extinction coefficients from research lbetter match observed optical light scatteri• Corrects bias but increases scatter at som
Light Extinction using old and revised IMPR

0

50

100150200250300350

0 50 100 150 200 250 300 350

Measured Bsp

IM P R O V E B s p

Scatter plot of the old IMPROVE equation estimated

particle light scattering versus measured particle light 

s

cattering.

0

50

100150200250300350

0 50 100 

S p lit C o m p o n e n t M e th o d B s p

Scatter plot of the revise

particle light scattering 

s

Scatter Plot for GRCA using IMPROVE Algorithm

1

10

100

1000

1 10 100 1000

Measured Bsp

Predicted Bsp

Scatter Plot f

1

10

100

1000

1 

Predicted Bsp
Natural Conditions Estim

• NAPAP Visibility Report (Volume 24) [1990] author• Based on available IMPROVE network data and oth• Estimated contiguous East and West U.S. annual ave

loading for visibility-impairing aerosols [specified un

• [Well] Known to underestimate natural carbon• Adopted by EPA for “Estimating Natural Visibility C

“old” equation – regional haze monitoring guidance 

http://vista.cira.colostate.edu/improve/Publications/

GuidanceDoc

• Default Natural Haze Lev

els Sensitivity Assessment 

RPOs

• Ivar Tombach is doing the analysis• Initial findings were presented at a June 2005 works

http://

www.wrapair.org/forums/aamrf/meetings/050

• Final report soon?
“Default” Natural Conditions Es

20% Best Days (left) & 20% Worst 
What should be done [if anything] wi

Natural Conditions Estimate

• Knowing the unknowable –

April 4, 2006

–

Inter-RPO 

Data Discu

ssion Group analysis presentation on revi

estimates u

sing the new IMPROVE algorithm and a 

approach –

Ames & Pitchford

• Things to think about:

– Natural conditions vary continuously in space and time –

do 

better estimates for planning purposes?

– Th

e w

o

r

st an

d b

est visibility d

ays’ d

efault natural co

n

ditions 

from measured dis

t

ributions of aerosol data –

these are for t

D

ECI

V

IEWS, n

ot for individual species –

how 

d

oes that line 

– How oft

en will we see frequent large OC/EC and Dust events 

years?

–

D

o w

e need to apply the revised IMP

ROVE equation to natu

– What monitoring period of record can be used to estimate na

– Can we make a better estimate of the distributions of w

orst a

years out, than John Trijonis did?

– What are the planning i

mplications of adjusting natural cond

down and changing the glide path for 116 Class I areas 

either for deciviews or individual species?

– Where d

oes take us for “demonstrating” reasonable progress 

– Mo

r

e que

s

tions ye

t t

o a

sked -
Next Steps on Natural Conditions 

the WRAP Region

• Attribution of Haze workgroup con

June 7th to review monitoring data 

http://www.wrapair.org/cal/calend

iew&id=552

• Plan to have AoH workgroup recom

WRAP region approach
http://vista.cira.colostate.edu/ts